The casting of molten materials is usually carried out using ceramic apparatus, ceramic molds, or receivers and apparatus. The choice of receiver material is critical in the casting of high purity materials and particularly critical in the casting of high purity silicon. In order to produce a cast article having optimum characteristics, it is desirable to control the crystallization of silicon. Thus, a receiver material which has thermal expansion characteristics which closely match those of the cast material is desired. Use of such a receiver material reduces the application of stress to the partially solidified or solidified cast material due to differential thermal expansion between the casting and the receiver.
It is an object of the present invention to produce a receiver which can be used in the casting of high purity silicon bricks.
An additional object of the present invention is to produce recievers that have low permeability to the casting material, sufficient hot strength to withstand heavy loads, and relatively low thermal expansion characteristics so that interfacial stresses between the receiver and the cast article are minimized.
Still another object of the invention is to provide a receiver which retains its shape so that the cast article has dimensional consistency.
Still another object of the invention is to provide a receiver which will produce silicon bricks having highly columnar silicon crystal growth which will produce bricks having good electrical properties.